By lighting or illumination it is typically referred to the art of exploiting light in producing a decorative or functional effect.
Traditionally lenses for artificial, man-made light sources such as bulbs, LEDs (light emitting diode), etc. have been designed as simple, symmetrical elements of suitable material such as plastics or glass. FIG. 1 depicts a typical lens associated with a point-like light source such as a LED 108 from different angles. From the axonometric view 102 and top view 104 the uniformity of a contemporary lens structure can be easily investigated. Further with reference to a side view 106, such flat (the shown case), concave, or convex lens contains even surface or at most, it may incorporate a constant optically functional pattern such as micro grooves or gratings. Such solutions have been relatively straightforward to develop and fabricate while still functioning relatively well in terms of light transmission, coarse refraction and light source protection objectives, but from the standpoint of arisen contemporary requirements set for illumination what comes the energy efficiency, light pattern controllability, light fixture size, etc., these simple conventional lenses have clearly become sub-optimum and new solutions are required. The optics have seemingly lagged behind the development of the actual light sources such as LEDs and their various further forms.
The aforementioned controllability of light has indeed gained importance significantly during the last few decades. For example, in the context of so-called intelligent outdoor lighting, specifically street lighting, light output may be adaptively adjusted based on factors such as street usage and even road conditions. Lights that activate automatically in the dark have been around for a while now. Also timers have been used for turning lights on/off. Cameras, photoresistors or other sensors may be functionally connected to the lighting equipment for enabling dynamic control over the light sources via appropriate adjustment measures. Similar considerations may be applied to many different indoor lighting scenarios e.g. in industrial premises, offices, houses, public places, etc. not forgetting special environments such as underwater lighting.
By more sophisticated control of light sources, a multitude of benefits in terms of e.g. reduced energy usage and light pollution may be obtained.
Street lights have been commonly implemented as lampposts on the edge of a road. Traditional lamps such as HPS (high-pressure sodium) lamps that have been available for fifty years now have recently faced competition from more modern options including LEDs. LEDs are, as such, relatively durable and energy efficient regarding particularly their scotopic lumen efficiency, but in many ways the available large scale solutions adopting LEDs have so far still been immature and inadequate what comes to the overall illumination power or luminous flux, and also controllability. Therefore, there still remains much to do in the context of light optimization having regard to a myriad of conditions where lighting is generally preferred if not absolutely necessary.